1. Field of the Invention
The present invention relates to a motor and a blower.
2. Description of the Related Art
Thin blowers have often been installed in electronic devices, such as notebook personal computers, to cool interiors of cases thereof. Such a blower includes a centrifugal impeller, a motor arranged to rotate the impeller, and a casing arranged to accommodate the impeller and the motor. Once the motor of the blower is driven, the impeller is caused to rotate to generate an air current inside an electronic device. Thus, heat which radiates from an electronic component, such as a CPU, installed inside the electronic device is dissipated.
A thin motor of such a blower includes a holder made of a resin and arranged to hold a bearing. The holder may be defined on a small area of a plate defining a bottom surface of the casing by outsert molding. In this case, it is necessary to securely fix the holder made of the resin to the plate.
A technique for increasing the strength with which a plate and a holder made of a resin are fixed to each other in the case where the holder made of the resin is defined on the plate by outsert molding is described, for example, in JP-UM-A H07-036586. According to the technique described in JP-UM-A H07-036586, a plurality of projections are cut and bent upward from a stator base, and a bearing holder made of a resin is defined integrally with the stator base so as to embrace the projections (see, for example, claim 1 and FIGS. 1, 2, and 3 of JP-UM-A H07-036586).
As described above, in the case of the thin motor, it is necessary to locate the holder made of the resin on a small area of the plate. In the case where a lower surface of the holder is closed, it is possible to arrange, in a center of the lower surface of the holder, a gate through which the resin is injected when the outsert molding is performed. This enables the resin to smoothly flow into a mold. According to a structure described in JP-UM-A H07-036586, however, a resin injected on a lower side of the stator base needs to flow to a space on an upper side of the stator base via through holes arranged at positions away from a central axis of the holder. At this time, the projections bent obliquely upward above the through holes interfere with a flow of the resin.
Meanwhile, in the case where the lower surface of the holder is in an annular shape and has an opening in a center thereof, it is impossible to arrange a gate in the center of the lower surface of the holder. In this case, it is more difficult to cause the resin to evenly fill an entire cavity to define the holder, which has a decreased thickness portion.